USP <905> - Uniformity of Dosage Units

What it says

General Chapter <905> describes methodology for assessing uniformity of dosage units, using either content uniformity testing, direct measurement of active ingredient in individual units, or weight variation testing where appropriate, to confirm consistent dosing across a batch.

Paraphrased for plain-language clarity. Always verify against the current published regulation text.

What it means in practice

• This chapter directly addresses a fundamental patient safety question: whether individual dosage units within a batch consistently contain the intended amount of active ingredient, since even a batch that passes average assay testing could contain individual units significantly over or under-dosed.
• The choice between content uniformity and weight variation testing depends on specific product characteristics, and applying the less rigorous weight variation approach when content uniformity is actually required understates the real risk of content inconsistency.
• Statistical acceptance criteria for this testing are specifically designed to catch both average deviation and excessive individual unit variability, reflecting that a batch could pass on average while still containing individually problematic units.

What inspectors look for

• Whether the correct testing approach, content uniformity versus weight variation, was selected based on genuine product characteristics rather than convenience or cost.
• Whether uniformity testing results are evaluated using the full statistical acceptance criteria, not simplified to an average result that could mask individual unit variability.
• Whether uniformity trends over time, across batches, are reviewed for early signs of a developing process control issue.

Related regulations